UGT1A1 and colorectal carcinoma: This study aimed to inform an economic evaluation of UGT1A1 pharmacogenetic test by identifying the predominant advanced CRC treatment pathways in the UK NHS, focusing specifically on the composition and placement of commonly used irinotecan-based regimens, the clinical management of patients on irinotecan-based chemotherapy, the frequency of irinotecan-related diarrhoea and neutropaenia, and the resource implications associated with the management of patients experiencing irinotecan-related neutropaenia.